The present invention relates to a coupling, a tool, a cutting head, a holder, a shim and a method of coupling two tool parts together. In particular, the invention pertains to locking two tool parts together by a ridge-groove structure formed in opposing surfaces of the parts.
From German Document No. 34 46 455 there is previously known a turning tool having a coupling comprising two grooved surfaces forced together, whereby teeth of each surface enter grooves of the other surface to lock the surfaces together. The known tool has four teeth at the lower side of cutting insert which cooperate with corresponding grooves in the holder. The strain on each individual groove becomes large and the resulting wear leads subsequently to poor precision in the machining result. The same applies for a tool according to German Document C2-34 48 086 and German Document No. OS-19 50 718 which include radially projecting teeth.
Disclosed in U.S. Pat. No. 5,682,803 is another turning tool of the above type, wherein a lower side of a shim is provided with a fine pattern of protrusions intended to directly stamp a corresponding pattern into the holder during turning. Said stamping will however happen successively and therefore the screw which holds the cutting insert loses its clamping force and must be retightened. In addition the repetitive accuracy becomes bad when the shim is exchanged since it is almost impossible to find the original position again. Thus, a new stamping must be made whereby the locking effect deteriorates after each exchange.
Further reference is made to commonly owned U.S. application Ser. No. 08/849,616 (corresponding to Swedish Application 9404266-0) and U.S. application Ser. No. 08/945,908 (corresponding to Swedish Application 9501687-9), which show a tool with cooperating grooves and teeth provided in one direction.